This invention relates to a thermoplastic elastomer composition, and more particularly, to a thermoplastic elastomer composition which is excellent in flexibility and heat resistance while retaining the excellent characteristic features of an ionomer resin per se which are transparency, mechanical strength, impact resilience (rebound resilience) and moldability. Said thermoplastic elastomer composition can be utilized in food uses such as food packaging sheet, cap liner and the like; daily sundries uses; sports things such as ski boots, other ski things, golf ball coatings, core materials and the like; toy uses; stationary uses such as desk mat and the like; automotive exterior and interior trim uses such as bumper guard and the like; civil engineering and construction uses such as engineering sheets, water-proof sheets and the like; domestic appliances such as cleaning corner bumper, refrigerator door seal and the like; AV apparatus uses, O.A. business apparatus uses, footwear and garment uses such as shoe sole, top lift and the like; textile uses; medical apparatus uses; chemical and mining industry materials; packaging and transporting materials; materials for agricultural industry, livestock industry and fisheries; and the like.
Ionomer resins in which at least part of the carboxyl group of an olefin-unsaturated carboxylic acid copolymer has been neutralized with a metal ion are widely used in the above-mentioned fields utilizing excellent properties, for example, abrasion resistance, transparency, stretchability, heat-sealability, oil resistance, hygienic quality, impact resistance, elasticity, flexure resistance, toughness, mechanical strength, coatability, adhesiveness, moldability and the like. Since they are, however, thermoplastic resins having a relatively low melting point, they have such disadvantages that when they are placed at a high temperature during use or secondary processing they tend to be deformed or broken by heat. Moreover, in respect of flexibility, a further improvement has been desired.
In order to solving the above problems, it has been considered to polymer-blend a resin having excellent heat resistance with the above ionomer resin to impart heat deformation resistance to the ionomer resin; however, the ionomer resins generally lack consistency with almost all resins, so that the resulting blend exhibits a delamination phenomenon, sufficient toughness and impact resistance are not obtained, and the flexibility is not improved.
For example, Japanese Patent Application Kokai No. 63-170,442 proposes blending an acrylic resin with the ionomer resin; however, this can be used only on the assumption that delamination is caused, and the flexibility of the resulting composition is not improved. Japanese Patent Application Kokai No. 60-71,653 proposes blending a propylene copolymer with the ionomer resin; however, this does not solve the delamination and flexibility problems similarly to the above.
On the other hand, when a soft elastomer such as ethylene-propylene rubber or the like is blended, there is such a problem that the characteristics inherent to the ionomer resin are lost, for example, the resulting composition is not transparent and the strength thereof is remarkably reduced.
When a softening agent such as an oil, a plasticizer or the like is added, there is such a problem that the softening agent bleeds to the surface of the resulting molded article to impair the appearance of the molded article, and the amount of the softening agent used is limited. As a result, only a hard molded article is obtained.